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Research Papers

Geometry Control of the Deposited Layer in a Nonplanar Laser Cladding Process Using a Variable Structure Controller

[+] Author and Article Information
Alireza Fathi

Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canadaafathi@engmail.uwaterloo.ca

Amir Khajepour

Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canadaakhajepour@uwaterloo.ca

Mohammad Durali

Mechanical Engineering Department, Sharif University of Technology, Tehran, 14588-83171, Irandurali@sharif.edu

Ehsan Toyserkani1

Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canadaetoyserk@uwaterloo.ca

1

Corresponding author.

J. Manuf. Sci. Eng 130(3), 031003 (May 02, 2008) (11 pages) doi:10.1115/1.2823085 History: Received June 02, 2007; Revised November 08, 2007; Published May 02, 2008

This paper presents a closed-loop laser cladding process used in nonplanar deposition of desired metallic materials. In the proposed system, the deposited layer geometry is continuously controlled via a sliding mode controller (SMC). The controller, which uses the scanning speed as the control input, is designed based on a parametric Hammerstein model. The model is a parametric dynamic model with several unknown parameters, which are identified experimentally using the recursive least squares method. The designed SMC is robust to all model parameters’ uncertainties and disturbances. The results showed that the tracking accuracy improves and the chattering effect reduces if an integrator on the scanning speed is added to the controller. It was observed that this addition decreases the response speed. The performance of the proposed controllers was verified through the fabrication of several parts made of SS303-L. This verification indicates that the developed closed-loop laser cladding process can reduce stair-step effects as well as production time in rapid prototyping of functional parts created with the adaptive slicing technique.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 2

Experimental outputs of the system under varying step velocity input

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Figure 3

Structure of the proposed model

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Figure 4

Geometry of the melt pool

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Figure 9

Simulation responses of the process controlled by the first SMC without measurement noise: (a) control output and (b) control input

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Figure 10

Simulation responses of the process controlled by the first SMC with measurement noise: (a) control output and (b) control input

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Figure 11

Simulation responses of the process controlled by the second SMC without measurement noise: (a) control output and (b) control input

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Figure 12

Simulation responses of the process controlled by the second SMC with measurement noise: (a) control output and (b) control input

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Figure 13

Experimental result of the first SMC tracking performance: (a) plant output and (b) scanning speed command (boundary layer thickness ε=2)

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Figure 14

Experimental result of the first SMC tracking performance at different boundary layer thicknesses: (a) plant output, (b) scanning speed command, and (c) boundary layer thickness (ε)

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Figure 15

Experimental result of the second SMC tracking performance: (a) plant output and (b) scanning speed command (boundary layer thickness ε=2)

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Figure 1

Schematic of nonplanar laser cladding

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Figure 5

Schematic view of the melt pool, the powder jet, and the laser beam

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Figure 6

The experimental transient response of the 3D laser cladding process for a random shape scanning velocity: (a) output and (b) input

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Figure 7

Validation of the identified models using the experimental data of the process response (the input is the same as in Fig. 6)

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Figure 8

Block diagram of the closed-loop process

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Figure 16

The closed-loop system performance in fabricating a ramp shape part

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Figure 17

The closed-loop system performance in fabricating a sinusoidal shape part

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